DESCRIPTION: The National Household Survey on Drug Abuse (NHSDA) represents a major effort to monitor drug use in the population on an annual basis. In addition to patterns of drug use of legal and illegal drugs, information is also collected about symptoms of drug dependence. Except for the work conducted by our research group, the data on dependence symptoms have been little analyzed. This competing continuation proposal requests 31/2 years of support to carry out further analyses of multiple waves of the NHSDA to investigate selected issues related to substance dependence on four drug classes: marijuana, cocaine, cigarettes and alcohol. During the prior six years of support, we developed proxy DSM-lV definitions of substance dependence and investigated extent of drug dependence in the population in different sex, and racial/ethnic groups, the relationships of dependence to extent of use among adolescents and adults, comorbidity of psychiatric disorders, drug and mental health treatment among adults, and parental-child similarity on marijuana use and smoking. In this next period, four issues will continue to be investigated: (1) the relationship between dependence and progression along the developmental sequence of involvement in drugs; (2) the extent of familial similarity on drug behavior between parents and adolescents, siblings and spouses; (3) the comorbidity of use and dependence with selected psychiatric disorders among adolescents; (4) the natural history of nicotine dependence. Analyses will be conducted for age, sex and ethnic specific groups, and will be based on the 1999, 2000 and 2001 surveys (N=66,706- 70,000). The samples are almost evenly divided among 3 age groups, 12-17, 18-25 and 26 years old and over. Each survey will provide a large number of nationally representative familial dyads, about 6,000 parent-child, 4,400 sibling, and 500 marital pairs. The very large national samples of youths and minorities, the inclusion of data on nicotine, and the availability of familial dyads make possible age, gender and racial/ethnic-specific analyses, comparisons across drugs, and analyses of intra intergenerational similarity on drug use in the NHSDA rarely feasible in any other study. The research will extend our understanding of the extent of serious drug use in the nation, the etiology of substance dependence, the extent of treatment needs, the transmission of drug use across and within generations, and racial/ethnic differences in patterns of use, dependence, comorbidity and familial similarity in the population. Such questions by and large have not been treated in the epidemiological literature on drug use in the general population, which has focused almost exclusively on frequency measures of drug use.